Alpha and beta coma in drug intoxication uncomplicated by cerebral hypoxia

Four patients who were rendered comatose or stuporous by drug intoxication, but who were not hypoxic, are described. Three patients received high doses of chlormethiazole for alcohol withdrawal symptoms, and one took a suicidal overdose of nitrazepam. The patient with nitrazepam overdose and two of those with chlormethiazole intoxication conformed to the criteria of ‘alpha coma’, showing non-reactive generalized or frontally predominant alpha activity in the EEG. The fourth patient who was unconscious after chlormethiazole administration exhibited generalized non-reactive activity in the slow beta range. All four recovered completely without neurological sequelae following the withdrawal of the offending agents. The similarities between the effects of structural lesions and pharmacological depression of the brain stem reticular formation are discussed. It is suggested that in both situations disturbed reticulo-thalamic interactions are important in the pathogenesis of alpha coma. It is concluded that when this electroencephalographic and behavioural picture is seen in drug intoxication, in the absence of significant hypoxaemia, a favourable outcome may be anticipated